Denver Broncos running back Knowshon Moreno was arrested for drunk driving in Denver earlier this month ... and in an ironic twist of fate, cops say the license plate on his ride read "SAUCED."

According to the Denver PD, 24-year-old Moreno was driving his convertible Bentley on Feb. 1 when he was pulled over for doing 70 in a 45 ... in a construction zone.

Police say Moreno smelled like booze ... and when he performed poorly on a field sobriety test, they arrested him for DUI.

Cops say Moreno was "very respectful and polite."

The Broncos released a statement ... saying, "We take the incident involving Knowshon Moreno very seriously and are thoroughly reviewing this matter. Our organization will continue to gather information and closely monitor this issue while the legal process runs its course."